linux-kernel - RE: [BUG] BUG: kernel NULL pointer dereference at ttm_device

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Date: Tue, 23 Jan 2024 01:06:54 +0000
From: "Bhardwaj, Rajneesh" <Rajneesh.Bhardwaj@....com>
To: Steven Rostedt <rostedt@...dmis.org>, LKML <linux-kernel@...r.kernel.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>, "Kuehling, Felix"
	<Felix.Kuehling@....com>, "Koenig, Christian" <Christian.Koenig@....com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: RE: [BUG]  BUG: kernel NULL pointer dereference at
 ttm_device_init+0xb4

[AMD Official Use Only - General]

-----Original Message-----
From: Steven Rostedt <rostedt@...dmis.org>
Sent: Monday, January 22, 2024 6:19 PM
To: LKML <linux-kernel@...r.kernel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>; Bhardwaj, Rajneesh <Rajneesh.Bhardwaj@....com>; Kuehling, Felix <Felix.Kuehling@....com>; Koenig, Christian <Christian.Koenig@....com>; dri-devel@...ts.freedesktop.org
Subject: Re: [BUG] BUG: kernel NULL pointer dereference at ttm_device_init+0xb4

On Mon, 22 Jan 2024 18:15:47 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> >     ttm_pool_init(&bdev->pool, dev, dev_to_node(dev), use_dma_alloc, use_dma32); <<<------- BUG!
> >
> > Specifically, it appears that dev is NULL and dev_to_node() doesn't
> > like having a NULL pointer passed to it.
> >
>
> Yeah, that qxl_ttm_init() has:
>
>       /* No others user of address space so set it to 0 */
>       r = ttm_device_init(&qdev->mman.bdev, &qxl_bo_driver, NULL,
>                           qdev->ddev.anon_inode->i_mapping,
>                           qdev->ddev.vma_offset_manager,
>                           false, false);
>
> Where that NULL is "dev"!
>
> Thus that will never work here.

Perhaps this is the real fix?

I think the fix might be already applied to drm misc. Please see, https://lkml.iu.edu/hypermail/linux/kernel/2401.1/06778.html


-- Steve

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index f5187b384ae9..bc217b4d6b04 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -215,7 +215,8 @@ int ttm_device_init(struct ttm_device *bdev, const struct ttm_device_funcs *func

        ttm_sys_man_init(bdev);

-       ttm_pool_init(&bdev->pool, dev, dev_to_node(dev), use_dma_alloc, use_dma32);
+       ttm_pool_init(&bdev->pool, dev, dev ? dev_to_node(dev) : NUMA_NO_NODE,
+                     use_dma_alloc, use_dma32);

        bdev->vma_manager = vma_manager;
        spin_lock_init(&bdev->lru_lock);